Ride height adjustment system for a motor vehicle

ABSTRACT

A leveling system for maintaining a motor vehicle body at an established height above the ground including a shock absorber with a concentric coil spring. An annular spring seat engages one end of the coil spring and is slidable on the shock absorber. The seat also forms a part of an expansible chamber that may be pressurized to increase the load on the coil spring and compensate for a change in vehicle loading. The system includes a fluid pressure source to pressurize the expansible chamber and a leveling valve assembly for depressurizing the expansible chamber.

United States Patent Graef 1 Aug. 29, 1972 [54] RIDE HEIGHT ADJUSTMENT SYSTEM [56] References Cited FOR A MOTOR VEHICLE UNITED STATES PATENTS [721 Km Germany 3,178,167 4/1965 Loewis ..280/124 F [73] Assigneez Ford Motor Company, Dearbom, 3,153,425 10/1964 Brueder ..280/ 124 F Primary Examiner-Philip Goodman [22] Filed: June 2, 1970 Attorney-John R. Faulkner and Clifiord L. Sadler I Related [15- Appli i n Data A leveling system for maintaining a motor vehicle body at an established height above'the ground includ- [60] Dmslon of 'Ser' 8 Sept' ing a shock absorber with a concentric coil spring. An abandoned Commuauon of 6 annular spring seat engages one end of the coil spring July 1970 31628310 and is slidable on the shock absorber. The seat also I forms a part of an expansible chamber that may be U-S. F, D s iz d to increase the load on the coil spring and [51] Int. Cl ..B60g 11/58 compensate for a change in vehicle loading, The [58] Field of Search ..280/124 F; 267/34, 65 D system includes a fluid pressure source to pressurize the expansible chamber and a leveling valve assembly for depressurizing the expansible chamber.

7 Claims, 4 Drawing Figures RIDE HEIGHT ADJUSTMENT SYSTEM FOR A MOTOR VEHICLE BACKGROUND OF THE INVENTION The present invention relates to a level or riding height adjustment for motor vehicle suspension systems in which the suspension unit consists of a shock absorber and a concentric coil spring.

A level or ride height adjustment for motor vehicles with-a hydraulic suspension unit is known in the art from German Published Patent Application No. 1,154,359. 154,359. The cylinder of the shock absorber of such a unit contains a suspension piston which is connected to the wheel suspension in addition to the standard shock absorber piston connected to the chassis.

The cylinder of the shock absorber is connected to the chassis of the motor vehicle by a spring element, such as a concentric coil spring. Level adjustment can be affected in this construction by an appropriate change in the shock absorber charge or pressure by a pump provided in the vehicle and by automatic or manually controlled regulating equipment.

A suspension unit of this type has the disadvantage that the seal of the suspension piston in the cylinder of the shock absorber is dynamically highly stressed due to the high alternating pressures occurring in the working or pressure chambers of the shock absorber. Seal ing at this point consequently is difficult and expensive and is subject to excessive wear.

German Publisher Patent Application No. 1,091,881 describes a level adjustment for motor vehicles in which the pressurized fluid required for a leveling unit is supplied by a hydraulic pump which is constantly actuated by the jounce and rebound movement of the vehicle. This type of level adjustment mechanism has the disadvantage that the hydraulic pump actuated by the movement of the vehicle suspension constantly oscillates about its center position whereby undesirable high wear occurs in that area.

It is the aim of the present invention to eliminate the disadvantages of the known level adjustment mechanisms and to provide a leveling system that is simple, inexpensive and reliable, and which furthermore has the advantage that it can be subsequently installed as a unit in a motor vehicle equipped with standard hydraulic shock absorbers.

BRIEF DESCRIPTION OF DISCLOSURE In accordance with the present invention, a height adjustment device for a motor vehicle is provided by a unique combination having the following characteristics:

b. The annular pressure chamber formed between the cylindrical sleeve and the cylindrical piston can be charged with a pressurized fluid by a hydraulic pump which is actuated only upon demand.

\ c. The line leading from the hydraulic pump to the annular pressure chamber contains a valve which blocks return flow through the line when the vehicle is at its correct height and which opens the line after a load is removed from the vehicle until the normal level is again reached.

The hydraulic pump may consist of a simple pump actuated by hand or foot pressure by the driver when a need indicated by a signal from the control valve or it can be an automatic pump actuated by suspension movement of the vehicle. In the automatic pump, the piston is equipped with an elastic rubber buffer which is spaced at a certain distance from the axle when the vehicle is at its normal or designed level, so that the pump is only actuated by a demand indicated by the lowering of the vehicle body and the rubber buffer BRIEF DESCRIPTION OF THE DRAWINGS The details, of the preferred embodiments of the present invention will be explained with reference to the accompanying drawings in which:

FIG. 1 is an elevational view, partly in section, of a hydraulic pump which can be utilized for a level adjust ment system according to the invention;

FIG. 2 is a schematic representation of a control valve assembly which can be utilized for a level adjustment system according to the invention;

FIG. 3 is an elevational view of a combination shock absorber, coil spring and height adjustment device constructed in accordance with the present invention; and

FIG. 4 is a schematic representation of an automatic hydraulic pump which can be used in a level adjustment system according to the invention.

DETAILED DESCRIPTION OF THE PREFERRED EMBODIMENTS FIG. 1 shows a hydraulic pump, the piston 1 of which is actuated in the cylinder 2 by the driver by hand or foot pressure. A pressure line 3 is constructed to carry the pressurized fluid displaced by piston 1 to the control valve assembly of FIG. 2 and the height adjustment device of FIG. 3. Piston l is returned to its initial position by a compression spring 4. A return flow bore 5 allows the pressurized fluid to return to the reservoir 10 during lowering of the height adjustment device. The reservoir 10 is connected to atmospheric pressure by the vent 77. A valve spring 6 forces a replenishing valve element 7 against its its seat except during the intake or return stroke of piston 1. A pressure relief valve8 is provided inthe. valve 7'which is forced by spring 9 against the overpressure valve bores 12. Reservoir 10 is connected to cylinder 2 by a bore 13.

FIG. 2 shows the arrangement of the control valve assembly. A check valve 21 is placed between the line 3 coming from the hydraulic pump and the lines 3a and 3b leading to left and right height adjusting devices of the type shown in FIG. 3. A shut-off valve 20 and a throttle valve 19 are installed parallel to the check valve 21 by T-connectors 22 and 23. The shut-off valve 20 is actuated by a valve arm 16 which is connected by spring to the chassis 14 of the vehicle and by a pull cable 17 connected to axle 18 of the vehicle.

In FIG. 3 a standard telescopic shock absorber 24 has been equipped with a cylindrical sleeve 25 at the lower end of its cylinder. The piston rod of the shock absorber 24 is connected'to a collar 26 which forms a spring seat and is secured by it to the chassis. A second spring seat or collar 28 supporting the other end of a coil spring 27 is mounted on the cylinder of shock absorber 24 in a sliding manner. A circular extension 30 of the second spring collar 28 forms a piston and together with cylindrical sleeve 25 defines a pressure chamber 31 which is sealed to the outside by a seal 32. Excessive upward movement of the piston 28 is prevented by a stop 33 on the shock absorber'24. The pressure chamber 31 can be charged with pressurized fluid by line 3a.

FIG. 4 shows another hydraulic pump which is actuated not manually by the driver as is the device of FIG. 1 but by the natural movements of the vehicle suspension elements.

A piston 1' moves in a cylinder 2 which is attached to the chassis of the motor vehicle. A compressionspring 4 biases piston 1 into its lower starting position. A pipeline 3' connects the pressure chamber of cylinder 2' with the height adjustment device of FIG. 3.

The pressure chamber of cylinder 2' is connected by' OPERATION At the normal level of the vehicle, the valve arm 16 of the shut-off valve oscillates about the position A (see FIG. 2) and, in that position, the return of pressurized fluid from the equalizing elements is blocked. If the vehicle is loaded and if the chassis 14 drops to such an extent with respect to axle 18 that a level adjustment becomes necessary for reasons such as ride comfort or headlightadjustment, the spring 15 pulls valve arm 16 from the position A to position C, whereby a switch 34 is closed. Switch 34 actuates a signal light that notifies the driver of the need for a level adjustment. A delay relay must be placed between switch 34 and the signal light in order to avoid actuation of the signal light during ordinary spring deflection. The signal lamp should only light up when the contact is closed over an interval of several seconds.

The driver will operate the hydraulic pump according to FIG. 1 upon observing the signal and force pressurized fluid by lines 3, 3a and 3b into the pressure chambers of the height adjustmentdevices of FIG. 3 until the coil springs 27 are stressed by raising the spring seat 28 to such an extent that the normal level of the vehicle is again reached. The valve arm 16 will then be returned 'to oscillate in the central range A by the pull cable 17 and the signal lamp will be extinguished.

In the. embodiment of the level adjustment system employing the automatic pump shown in FIG. 4, the switch 34 is no longer necessary because piston l 'of the pump automatically contacts the axle 18 with its elastic rubber buffer 35 when its deflection exceeds the amount S and thereafter the pump is operated upon each jounce movement of the axle 18 to supply pressurized fluid to the pressure chambers of the devices of FIG. 3. Once the standard level of the vehicle has been attained, due to the stress of the vehicle coil springs 27, the pump of FIG. 4 will automatically stops its delivery until such time as the axle 18 deflects through the distance S.

If a loaded motor vehicle raised to its normal level is unloaded, the chassis 14 will then be spaced from the axle 18 by an undesirable excessive amount and the pull cable 17 will place valve arm 16 of the shut-off valve 20 into the position B. In this position, shut-off valve 20 opens and the return flow of pressurized fluid from the annular pressure chamber 31 passes through W the throttle valve 19, line 3 and return bore 5. Chassis 14 thus drops-slowly with respect to the axle 18 until valve arm 16 is again returned to the A position by spring 15 whereupon the shut-off valve 20 closes again. The foregoing description presents the presently preferred embodiments of this invention. Alterations and modifications may occur to those skilled in the art that will come within its scope and spirit.

I claim: l 1. A ride height adjustment system for a motor vehicle comprising an extendible strut, said strut having an expansible chamber constructed to increase the length of said strut when pressure fluid is conveyed to said chamber, a fluid pressure source, means connecting said source to said chamber, said means including a valve assembly, said valve assembly comprising a check valve constructed to prevent fluid flow from said chamber to said source while permitting flow from said source to said chamber, said valve assembly also comprising a control valve in parallel circuitry with said check valve having a valve element constructed to remain in a closed position when said strut is extended a preset amount and to move to an open position when said strut is extended beyond said preset amount to permit fluid flow out of said chamber.

2. A ride height adjustment system for a motor vehicle according to claim -1 and including: a

a throttling means in parallel circuitry with said check valve and in series with said control valve. 3. A ride height adjustment system for a motor vehicle according to claim 1 and including:

manual means for actuating said fluid pressure source, signaling means constructed to convey information to the operator of said motor vehicle regarding the relative position of the sprung and unsprung components of said vehicle whereby said operator may manually actuate said fluid pressure source to increase the ride height by increasing the length of said strut when said signaling means indicates such a need. 4. A ride height adjustment system for a motor vehi cle having sprung and unsprung components, spring means interposed between said components and including an expansible chamber device constructed to adjust the relative position of saidsprung and unsprung components, a fluid pressure source, means connecting said source to said expansible chamber, said means including a valve assembly, said assembly comprising a check valve constructed to prevent fluid flow from said chamber to said source while permitting flow from said source to said chamber, said valve assembly also comprising a control valve in parallel circuitry with said check valve, means constructed to maintain said control valve in a normally closed position when said sprung and unsprung components are separated by an amount exceeding said preset distance to thereby permit fluid flow out of said chamber.

5. A ride height adjustment system for a motor vehicle according to claim 4 and including:

said fluid pressure source having manual means for creating fluid pressure, said system including.

signaling means constructed to convey information to an operator of said vehicle that said sprung and unsprung components are separated by an amount less than said preset distance whereby said manual means of said fluid pressure source may be actuated to cause fluid to flow through said check valve into said expansible chamber and increase the separation of said components. 6. A ride height adjustment system for a motor vehicle according to claim 4 and including:

said fluid pressure source including automatic pump means constructed to create fluid pressure automatically when the distance between said sprung and unsprung components falls below said preset distance. 7. A ride height adjustment system for a motor vehicle according to claim 6 and including:

said automatic pump means comprising first and second pump members, said members defining a pump chamber, means connecting said pump chamber to said expansible chamber, one of said members being connected to one of said components and the other of said members being constructed to engage the other of said components, said members being relatively movable to expel fluid from said pump chamber when the distance between said components falls below said preset distance. 

1. A ride height adjustment system for a motor vehicle comprising an extendible strut, said strut having an expansible chamber constructed to increase the length of said strut when pressure fluid is conveyed to said chamber, a fluid pressure source, means connecting said source to said chamber, said means including a valve assembly, said valve assembly comprising a check valve constructed to prevent fluid flow from said chamber to said source while permitting flow from said source to said chamber, said valve assembly also comprising a control valve in parallel circuitry with said check valve having a valve element constructed to remain in a closed position when said strut is extended a preset amount and to move to an open position when said strut is extended beyond said preset amount to permit fluid flow out of said chamber.
 2. A ride height adjustment system for a motor vehicle according to claim 1 and including: a throttling means in parallel circuitry with said check valve and in series with said control valve.
 3. A ride height adjustment system for a motor vehicle according to claim 1 and including: manual means for actuating said fluid pressure source, signaling means constructed to convey information to the operator of said motor vehicle regarding the relative position of the sprung and unsprung components of said vehicle whereby said operator may manually actuate said fluid pressure source to increase the ride height by increasing the length of said strut when said signaling means indicates such a need.
 4. A ride height adjustment system for a motor vehicle having sprung and unsprung components, spring means interposed between said components and including an expansible chamber device constructed to adjust the relative position of said sprung and unsprung components, a fluid pressure source, means connecting said source to said expansible chamber, said means including a valve assembly, said assembly comprising a check valve constructed to prevent fluid flow from said chamber to said source while permitting flow from said source to said chamber, said valve assembly also comprising a control valve in parallel circuitry with said check valve, means constructed to maintain said control valve in a normally closed position when said sprung and unsprung components are separated by an amount exceeding said preset distance to thereby permit fluid flow out of said chamber.
 5. A ride height adjustment system for a motor vehicle according to claim 4 and including: said fluid pressure source having manual means for creating fluid pressure, said system including signaling means constructed to convey information to an operator of said vehicle that said sprung and unsprung components are separated by an amount less than said preset distance whereby said manual means of said fluid pressure source may be actuated to cause fluid to flow through said check valve into said expansible chamber and increase the separation of said components.
 6. A ride height adjustment system for a motor vehicle according to claim 4 and including: said fluid pressure source including automatic pump means constructed to create fluid pressure automatically when the distance between said sprung and unsprung components falls below said preset distance.
 7. A ride height adjustment system for a motor vehicle according to claim 6 and including: said automatic pump means comprising first and second pump members, said members defining a pump chamber, means connecting said pump chamber to said expansible chamber, one of said members being connected to one of said components and the other of said members being constructed to engage the other of said components, said members being relatively movable to expel fluId from said pump chamber when the distance between said components falls below said preset distance. 